1. Field of the Invention
The present invention relates to an ink jet recording apparatus which performs ink jet recording on a recording material (recording medium) with an ink jet recording means, and more specifically relates to an ink jet recording apparatus provided with a conveying means for conveying a recording material which can generate concave and convex deformation.
2. Related Background Art
As a recording apparatus having a function such as a printer, a copier, a facsimile or the like, or a recording apparatus used as an output apparatus such as a composite type electronic apparatus or a work station including a computer or a word processor or the like, an ink jet recording type apparatus which discharges ink onto a recording material (recording medium) such as paper, cloth, a plastic sheet, an OHP sheet or the like based on image information (recording information) to perform recording is becoming widespread. Further, there are various needs for qualities of these recording materials. Recently, developments for these needs have been made, and recording apparatuses, which record on cloth, leather, a nonwoven cloth, or metal or the like, as well as paper including thin paper or processed paper, or a resin sheet (OHP sheet and the like) or the like, which are usual recording materials, are also used.
In the above-mentioned recording apparatuses such as a printer, a copier, a word processor, a personal computer, a facsimile, and the like, a conveyance mechanism for the recording material, provided with a conveying roller for conveying the recording material, a plurality of pinch rollers arranged in a straight line for pressing against the conveying roller, a plurality of expelling rollers arranged in a straight line for expelling the recorded recording material, a plurality of expelling spurs (expelling rotary members) arranged opposingly to the paper expelling rollers for expelling the recording material, is used.
FIG. 8 is a partial plan view showing the main portion of a recording material conveying mechanism of a conventional recording apparatus. In FIG. 8, a recording material (not shown) is sandwiched between a conveying roller 4 and a pinch roller 5 split in plural portions and is recorded while it is conveyed along a platen 10 arranged opposingly to a recording portion. A recorded recording material (not shown) is expelled while being sandwiched between expelling rollers 11 and expelling spurs (expelling rotary members) 12. As shown in FIG. 8, the expelling rollers 11 and the expelling spurs 12 are positioned in the width direction (a direction perpendicular to the conveyance direction of the recording material) of the recording material (not shown) so that respective pairs are opposed to each other. In the configuration of FIG. 8, paper holding spurs (paper holding rotary members) which will be described later are not provided.
Japanese Laid-Open Patent Application No. 59-188467 describes an ink jet printer which conveys a paper to a position opposed to an ink jet printing head with a platen roller and two pinch rollers which sandwich the vicinities of both ends of the paper respectively, and prevents lifting of the paper from the platen roller with a roller having a number of saw-tooth protrusions between two paper holding rollers which sandwich the vicinities of the both ends of the paper respectively at the downstream side, thereby to prevent contact between the printing head and the paper. However, since the paper is pressed with the platen roller only in the vicinities of both ends and the roller having the saw-tooth protrusions is spaced from the platen roller, contact between the printing head and the paper cannot be positively prevented. Particularly, in a case where an amount of application of ink droplets to the paper is significantly increased as in full-color printing and the like, such problems remarkably occur.
Japanese Laid-Open Patent Application No. 9-193373 discloses an ink jet printer provided with paper holding spurs for holding the recording material so as to prevent recorded recording material from being deformed into a convex shape. The paper holding spurs have no opposed expelling rollers. Further, a recording apparatus has also been provided, which is formed so that expelling of the recording material is carried out while controlling generation of concave and convex shaped deformations in the recording material (so called cockling), by providing a paper holding spur having no opposed expelling roller with a pressing means and always pressing the recording material to previously deform the recording material portion opposed to the paper holding spur to a concave shaped portion. FIG. 9 is a partial plan view showing the main portion of a conventional recording material conveying mechanism provided with paper holding spurs having no opposed expelling rollers.
However, such conventional recording material conveying mechanisms as shown in FIGS. 8 and 9 have the following disadvantages. First, in such a conveying mechanism having no paper holding spurs as shown in FIG. 8, a convex shaped deformation of the recording material easily occurs at the downstream side portion of a gap portion between adjacent pinch rollers in the recording material conveyance direction, and the recording material is brought into contact with a recording means (recording head) whereby the recording surface of the recording material is stained.
Second, even in a conveying mechanism provided with paper holding spurs 14, in a case where split pinch rollers 5 are provided as shown in FIG. 9, the positions of pinch rollers 5 which press the upstream side of the recording area in the recording material and the positions of expelling spurs 12 and paper holding spurs 14 which press the downstream side thereof are in the width direction of the recording material. As a result, the positions where the recording material is pressed are defined with pitches having no interrelationship between the upstream side and the downstream side of the recording area. Thus, the balance of positions where the recording material is pressed is bad. Accordingly, even if paper holding spurs are placed at the downstream side, the recording material is deformed in a concave (not convex) shape in the recording area and positions of occurrence of concave and convex portions due to cockling of the recording material cannot be controlled. As a result, the recording material is brought into contact with a recording head whereby the recording surface is stained.